Wireless transmitters can be configured to transmit information that can be used to determine a location of a mobile device and provide content to a mobile device based on the mobile device's location. For example, GPS, Wi-Fi, and cellular transmitters all provide information that can be used to determine the location of a mobile device. Known locations of wireless transmitters and distances between the wireless transmitters and a mobile device (e.g., derived from signal strength) can be used to perform trilateration to determine a specific location of the mobile device. Geofencing based on the location and transmission range of one or more wireless transmitters can be used to determine when a mobile device enters or exits a geofenced area.